So I know during the freljord event every clan got really cool "logos". I find that Piltover is my favorite area of League so much so I named my kitten 
! This being said I've been trying to plan out a sleeve tattoo of video games I like thus league of legends needs to be in there and to do this and to give a extra nod to my kitten I wold like a piltover logo.
So basically, is there a logo that someone (hopefully Riot) has made?
The point of Freljord logos was, that you could choose which tribe you want to reign over Freljord. If Ashe an Tryndamere or Gragas, or Sejuani and Olaf, or Lissandra and Trundle.
The logos represents the tribe's name, spirit and the ancestors, of which all three princess (Lissandra, Ashe, Sejuani) are descendants.
Since Piltover is a city with steampunk, which refers to the good side - while Zaun represents the bad side. However, Piltover is no real city, it's more of a academic institution, which doesn't take part in the war of Valoran, but assists by exploring and building new environment to secure the victory.
However, I don't think that there is any logo, because it's a neutral "city" and not a tribe or a strategic point with an army like Demacia, Freljord, Ionia, Bandle City or Noxus.
Piltover has just some individuals which stand out of the neutral city.
I've tried to find something though. You see the logo in the picture of Vi's artwork, on the left side, a bit hidden by a blue pipe? http://fanboygaming.com/wp-content/uploads/2012/12/Vi_splash.jpg
I thought first that it could be a logo, but by looking at Jinx's artwork: http://static.squarespace.com/static/50d0fc0ae4b0c75e54db0249/t/525cd06ee4b048ac9edbbbb5/1381814383389/jinx_splash_10.jpg It's too different to be a important logo that represents Piltover, so I guess it's not what you are looking for.
you could workaround it with this here that I've found: http://lol.replays.net/story/issue4/PiltoverCustoms_logo.jpg Or http://www.wallsave.com/wallpapers/1600x900/caitlyn/2106667/caitlyn-lol-piltover-s-finest-vi-and-wp-by-xrazerxd-fan-art-2106667.jpg
Sorry if I couldnt help you.
